I think the signal to noise ratio has decreased, but that doesn't mean there's less signal; there's just a lot more noise.
Back in the 80s and 90s you were cherry picking the elite and the intellectuals, the internet of back then was never going to be representative sample of humanity
20 years ago there were definitely less garbage on the Internet, and less gems as well.
But I definitely agree with the movie part. We still get a few good ones here and there but it's kind of rare nowadays :(
The current internet content is made for the internet. A lot of great things were made of course but I think the optimisation is diluting it into mediocracy. Every single day it gets more and more optimised for revenue or influence through time dominance. If you pay for it, it is designed to keep you pay for it(not necessarily pay for it and consume it but keep paying. Games are mostly freemium where you pay if you want to enjoy, movie subscription services will pile sh*t in font of you to give you the impression of endless content, optimize scenarios for retention etc.). If it is free, it is designed to pay by proxy(purchase something or give political power to an interest group).
Go back past the search engines, and most knowledge simply wasn't on the internet yet.
On the contrary, I would argue that the content quality is drastically lower because of optimisation for revenue and much less purer motivations.
The video quality is really much much better though. Original video scene is great as the business side of the things is a solved problem. Yet again, it suffers from optimisation for advertisers as less and less things are kosher.
Oh and the movie scene is terrible IMHO as a whole, despite having some amazing movies. Netflix is also optimising and the most optimum content for the business of Netflix is often not that optimum for many people. Not many tall poppies came out of it.
It's funny how a pop singer made a song about our optimised happy lives: https://www.youtube.com/watch?v=Um7pMggPnug